In a conventional method of measuring a degradation degree of the aging insulating oil in an electric apparatus, sampled materials which have been used for a long time are tested generally by a method of analyzing acid value, applying a breakdown voltage and analyzing a resulting gas at the laboratory, without testing them immediately on the spot, and therefore it has a problem of delay since it is not on the spot testing, as well as a problem in accuracy of the tested value. Produced materials from the aging insulating oil of the electric apparatus generally consist of the gas and the particles of impurity.
Accordingly, a gas analyzing test developed at present and hydrogen gas detection are kinds of measuring methods for the amount of the produced gas. In the analyzing method of the gas produced in the insulating oil of the electric apparatus, the gas ingredient is analyzed by the varied amount of resistance generated between both ends of the electrodes when the gas particles pass through a gas barrier contacted with the porous electrodes.
Therefore, the problems occurring in gas analyzing methods are a great variation of the tested value as well as low reliability of the test result in accordance with the environmental circumstances, because of the nature of the active gas, and also it is a drawback not to be used in general except in big facilities, because the gas analyzing equipments require installation of very expensive chemical accommodations.
In addition, the samples to be tested are taken on the spot in analyzing acid value and applying breakdown voltage, and thereby there is a fear of penetration by air and moisture and due to the above sensor there are lots of problems such as error occurrence of the tested value, low reliability of the tested result by testing in exposure of the air, and the limited apparatuses to be tested.